SRE30: private repo on GitHub mentioned in the material is not accessible

Similar as https://github.com/microsoft/IgniteTheTour/issues/24 ,
the following repository mentioned in https://github.com/microsoft/IgniteTheTour/tree/master/SRE%20-%20Operating%20applications%20and%20infrastructure%20in%20the%20cloud/SRE30 is not accessible:
```
# This repo has the database schema scripts
git clone https://github.com/Azure-Samples/tailwind-traders
```
